The invention relates to improvements in fluid couplings, particularly to improvements in so-called quick connect/disconnect coupling devices. Still more particularly, the invention relates to improvements in coupling devices wherein a sleeve-like tubular connecting or coupling member can be permanently or separably connected with an end of a first conduit (such as a flexible hose) and the coupling member can be separably connected to an end of a second conduit (e.g., a pipe, a tube or a nipple) by establishing with the end of the second conduit a form-locking connection.
It is already known to provide a coupling device of the above outlined character with a locking element which serves to releasably hold the components of the form-locking connection in engagement with each other. This enhances the reliability of the coupling device because the coupling member is less likely to become accidentally separated from the end of the second conduit. The locking element can comprise a ring which is movable along the coupling member between an inoperative position in which the form-locking connection can be terminated and an operative position in which the form-locking connection is effective to maintain the coupling member in engagement with the end of the second conduit.
Commonly owned U.S. Pat. No. 5,226,680, Bahner et al., issued Jul. 13, 1993. discloses an indicator in the form of an elastic tongue which is of one piece with the tubular coupling member. The latter has a recess for its tongue and, when the tongue is in unstressed condition, it acts as a stop or barrier to oppose the movement of a locking ring from the operative to the inoperative position. The tongue can be moved radially inwardly of the tubular coupling member to thus permit the locking ring to move thereover at least partly to the retracted or inoperative position in which the coupling member can be disengaged from the end of the second conduit. The locking ring permits inspection of the tongue when it assumes the operative position (i.e., when the coupling member is properly connected with the end of the second conduit) but conceals the tongue when it is caused to leave the operative position or is yet to reach the operative position. Thus, the person or the instrument carrying out a final inspection-of the condition of form-locking connection between the coupling member and the second conduit can ascertain whether or not the form-locking connection has been established. Problems arise if the patented coupling device is to be installed at a location (e.g., under the hood of a motor vehicle) where the tongue is not readily visible or is not visible at all. Under such circumstances, the condition of the form-locking connection between the coupling member and the end of the second conduit cannot be ascertained at all or can be ascertained only with the expenditure of a substantial amount of time. The situation is analogous if the patented coupling device is installed in such orientation or in such angular position that the major part of the coupling member conceals (e.g., overlies) the tongue irrespective of the position of the locking ring.
U.S. Pat. No. 4,946,205, Washizu, issued Aug. 7, 1990, discloses a coupling device wherein the tubular coupling member serves to separably connect one end of a hose with one end of a pipe. The coupling member and the pipe establish a form-locking connection as soon as the coupling device is properly assembled. The coupling member is provided with two slots which are disposed diametrically opposite each other and receive protuberances provided on the prongs of a sleeve which is installed in the coupling member. The prongs form part of the form-locking connection in that they engage an external rib of the pipe when the latter is properly inserted into the coupling member. The protuberances prevent separation of the prongs from the rib as long as they extend into the slots of the coupling member. The condition of the form-locking connection is indicated by a substantially C-shaped indicating member having two arms which straddle the coupling member and have portions extending into the aforementioned slots when the coupling member is not form-lockingly connected with the end of the pipe. At such time, the arms of the C-shaped indicating member cannot be separated from the coupling member and this indicates to a person inspecting the coupling device that the form-locking connection is yet to be established. On the other hand, when the form-locking connection is satisfactory, the portions of the arms are expelled from the slots by the protuberances of the aforementioned sleeve in the coupling member; the indicating member is then readily separable from the coupling member to thus indicate that the coupling device is properly assembled.
Washizu further proposes to employ a second substantially C-shaped indicating member which can be applied to straddle the coupling member and engages resilient prongs of the coupling member when the form-locking connection is incomplete so that the second indicating member is prevented from becoming separated from the coupling member. The prongs of the coupling member do not interfere with detachment of the second indicating member when they properly engage the external rib on the end of the pipe, i.e., when the form-locking connection is operative. Thus, the two indicating members are respectively disengageable from the slotted portion of the coupling member and from the prongs only and alone when the coupling member properly engages the external rib of the pipe.
A drawback of the coupling device which is disclosed by Washizu is that it does not embody any means for maintaining the form-locking connection in the operative condition. Thus, the connection can be terminated in response to a pronounced pull upon the pipe in a direction to extract it from the adjacent end portion of the coupling member, i.e., to disengage the prongs from the rib. The indicating member or members merely serve to inform the person in charge of the condition but not of the reliability of the form-locking connection. The condition of the connection can be ascertained by attempting to detach the indicating member or members from the coupling member; if the indicating member or members are detachable, the connection is operative. The person in charge can also decide to merely touch the indicating member or members in order to ascertain the position of such indicating member or members relative to the coupling member.